"The applicants have failed to address in any meaningful way the competitive showing traditionally required by the FCC when reviewing major transactions," the petition reads. "Because the applications are therefore facially defective, they should be denied."

Backed by $3.2bn from Intel, Google, Comcast, Time Warner Cable, and Bright House Networks, Sprint and Clearwire have agreed to merge their beleaguered WiMAX networks under the control of a brand new company, also called Clearwire. Together, the two operations hope to blanket the States with "4G" wireless well before the likes of AT&T and Verizon, delivering the mobile internet to laptops and various consumer electronics devices as well as phones.

Sprint's network has rolled out slower than expected. Clearwire's network was originally designed for fixed-location wireless access, not mobile. And the companies' definition of 4G may not cut the mustard. But AT&T stills sees the merger as a threat.

"Clearly, a company that has the largest spectrum position of any mobile carrier, deploying a service that is 'here now,' with financial backing from Google, Intel, and three of the nation’s largest cable television companies is capable of substantially impacting competition in the mobile communications market," continues AT&T's petition.

It's worth noting that the joint Sprint-Clearwire network will be open to any device and any application. Though AT&T likes to say that it has fully embraced openness, this may or may not be true.

According to a message tossed our way by a company spokesman, AT&T "does not fundamentally oppose the transaction." It simply believes that "Sprint and Clearwire should be required to demonstrate that its merger serves the public interest just like any other providers would have to do."

The company argues that in seeking FCC approval for their tie-up, Sprint and Clearwire haven't put all their cards on the table. The FCC requires added scrutiny for transactions that would deliver an unusually large swath of spectrum to a single operation, and AT&T claims that the "New Clearwire" has failed to disclose all its holdings in a portion of the US airwaves known as the Broadband Radio Service (BRS) and Educational Broadband Service (EBS) spectrum.

The BRS/EBS spectrum was originally licensed to American schools and colleges for on-campus broadcasting. But in recent years, the FCC has shifted the band to commercial use, letting those schools and colleges lease their holdings to corporate interests, including Sprint and Clearwire - and AT&T.

When the FCC reviewed AT&T's merger with Dobson last year, it did not scrutinize AT&T's BRS/EBS holdings because the band was still making the slow transition to commercial spectrum. But BRS/EBS is part of the 2.5GHz band where Sprint and Clearwire are deploying WiMAX. It only follows, AT&T tells the FCC, that commercialization is very much a reality.

"The applicants have touted this spectrum as being superior for the delivery of mobile broadband to the public. And the major reason the spectrum has not been previously included has evaporated - the applicants note that the BRS/EBS transition is 'nearly complete.'"